Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Despite no annotations, the description discloses key behaviors: the contract type (signed bearer token, unmetered access), freshness constraints, stateless verification, 402 fallback on expiry, pricing, and the fact that it is a verified observation feed with no win-rate claims. This adds significant context beyond the schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is relatively long and contains some redundancy (e.g., 'Same contract as the 24-hour pass over a 30-day window' could be trimmed). However, it is well-structured with line breaks for key points, and critical warnings are front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description lacks information about the tool's return value or output format (no output schema). The parameter is not fully documented. While the purchase use case is covered, the agent is left guessing what happens after a successful call (e.g., token delivery, confirmation).

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage, the description should explain the 'payment_signature' parameter. It mentions 'signed bearer token' in the contract description but does not explicitly link to the parameter or clarify its format or origin. The agent may infer, but it is not explicit enough.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Buy a 30-day unmetered pass') and the resource ('SYGNL/47 live tier'). It differentiates from sibling tools like sygnl47_subscribe_live_24h and sygnl47_subscribe_archive_30d by specifying the duration and tier.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly advises reading sygnl47_manifest first, providing a precondition for usage. Also notes that the tool is for purchasing and that the subscription is not a prediction, helping the agent decide when to use it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.